Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $92.95   4.464%   $97.0993   $97.10   $97.10   $97.10  
  Purchase #2 $193.60   9.124%   $211.2641   $211.26   $211.25   $211.30  
  Purchase #3 $165.46   5.310%   $174.2459   $174.25   $174.25   $174.20  
  Purchase #4 $224.58   10.239%   $247.5747   $247.57   $247.55   $247.60  
  Purchase #5 $237.50   6.830%   $253.7213   $253.72   $253.70   $253.70  
  Purchase #6 $61.95   7.427%   $66.551   $66.55   $66.55   $66.60  
  Purchase #7 $149.62   4.323%   $156.0881   $156.09   $156.10   $156.10  
  7 purchase totals = $1,125.66       $1,206.5444   $1,206.54   $1,206.50   $1,206.60